1. Field of the Invention
This invention relates to hand tools used to separate a first cable with a curved outer surface, such as a coaxial cable, from an adjacent cable or wire joined to the first cable by a connecting web of material. More specifically, this invention relates to tools that cut through the attaching web of material and to tools used to shave off excess web material from the curved outer surface of the first cable.
2. Description of Related Art
Coaxial cables are widely used in many different applications, particularly including the distribution of video signals. Although a single coaxial cable can carry a video signal, there are many applications where an additional cable or wire, referred to as the xe2x80x9cmessengerxe2x80x9d is needed.
For long suspended spans, the coaxial cable may be provided with a support wire, attached as a messenger wire to the coaxial cable. Messengered cable of this type commonly has the messenger wire positioned adjacent and parallel to the coaxial cable with both cables being encased in insulating coatings. The two insulated cables are connected together by a web of the same insulating material forming an integral side-by-side coaxial cable and messenger wire support.
In other applications, a second coaxial cable may be desired for redundancy or to increase signal carrying capacity. Multiple cable designs may also have twisted pair or multistrand control wires placed adjacent to coaxial cables. In each of these designs the cables are held in a side-by-side relationship by a web, usually formed out of the same material used to provide the outer cable insulation layer.
To use such cables, the web must be severed for some distance back from the end of the cable to free the coaxial cable from the messenger. This allows a connector to be attached to the coaxial cable. Where the messenger is a support wire, the web may need to be slit at a midpoint of the cable to allow the support wire to be attached to an intermediate support on a long span.
One method of separating the cables is to cut the web with a knife. However, this risks damage to the insulating coating if the knife wanders away from the centerline of the web as the cut is made.
To address this problem, longitudinal slitting devices have been designed that hold a cutting blade in the desired location relative to the cable while the tool is pushed or pulled along the length of the cable by the user to cut the web. In one design, the tool has a cylindrical hole approximately the diameter of the coaxial cable portion. A slot with a width just larger than the thickness of the web extends along the cylindrical hole, allowing the tool to pass over the coaxial portion of the cable while the messenger is still attached to it.
The cylindrical hole of the tool is in contact with and guides along the outer circumference of the coaxial cable portion as the user moves the tool lengthwise along the cable. A flat slitting blade is attached to the tool and positioned approximately tangential to the circumference of the coaxial cable. The blade needs to be positioned sufficiently far from the coaxial cable to avoid damaging it and sufficiently close to avoid leaving a large ridge of excess web material on the cable. Excess web material interferes with the proper attachment of a coaxial connector. It also interferes with the use of industry-standard coaxial cable preparation tools that guide on the expected cylindrical outer surface of the coaxial cable.
To produce an acceptable cut, the web-slitting blade needs to be configured to make a cut that is precisely tangential to the outer perimeter of the coaxial cable. Proper positioning of the single slitting blade relative to the outer curved surface of the coaxial cable is critical. However, It takes a relatively large force to make the first cut through the web. This force, and the fact that the insulation of the cable is slightly resilient, and the blade is relatively thick often causes the initial cut through the web to wander slightly producing further imperfections in the final exterior surface of the coaxial cable. To avoid damaging the coaxial cable insulation, the slitting blade may need to be positioned slightly farther from the true tangential position, however, this increases the size of the ridge of excess web material left by the slitting blade.
A further problem with this type of single blade slitting tool is that it must slide over a free end of the cable. This prevents its use at intermediate positions along the cable where the web must be slit to attach a messenger support wire to an intermediate support position, such as to a support pole on a long span.
To address these problems, yet another type of slitting tool has been developed which uses a slitting blade to make an initial cut through the web and a separate shaving blade to shave off the excess web material left by the initial cut. Further, this design uses a two-piece hinged tool body, which can open to receive the cable, allowing the web to be cut at intermediate points along the length of the cable. An example of a tool with this design is seen in U.S. Pat. No. 6,131,289, owned by the assignee of the present invention. A principal advantage for this tool design is that the initial cut, which may wander slightly, is made closer to the centerline of the web, instead of directly tangential to the coaxial cable. This prevents the initial cut from inadvertently wandering into and damaging the insulation of the coaxial cable. A larger excess of web material can be left, which the shaving cut can then remove with great accuracy along a plane that is tangential to the desired final cylindrical shape for the coaxial cable.
Despite these advances in slitting tool design, the described prior art tools and techniques do not meet all the needs of the industry. A key problem is that both single blade slitting tools and double blade slitting and shaving designs make the final removal cut with a flat blade, whereas the preferred final exterior surface for the coaxial cable is cylindrical. If the slitting or shaving blade is set exactly tangential to the desired external surface, it leaves a very slight longitudinal ridge of excess web material along the cable on both sides of the true tangent line. If the blade is set closer to the coaxial cable, it removes too much material and produces a longitudinal xe2x80x9cflatxe2x80x9d along the outside of the cable, by slicing along a chord through the circular cable cross section.
This ridge or flat can prevent an electrical connector from being properly attached to the cable or prevent a cable preparation tool from removing the right amount of insulation material prior to attaching the connector. Coaxial connectors and cable preparation tools are designed for use with coaxial cables having a circular, defect-free, cross section. Preparation tools that are used to remove insulation from a portion of the cable often guide their cutting blades on the outer surface of the cable. Such tools rely on the defect-free accuracy of the outer cable surface to ensure that the correct depth of cut is made without damage to the interior conductors in the cable. Connectors often use sealing gaskets intended to make a hermetic seal to the defect-free outer cable surface. Consequently, even if the cable is prepared accurately with a prior art tool, a ridge or flat on the cable may allow moisture to enter the attached connector and cause it to fail.
A final difficulty with prior art tools occurs when they are used on very stiff and inflexible large diameter messengered cables, particularly when such cables have a bend near the end of the cable being prepared. For single blade tools that rely on a single cylindrical hole in the tool body, the curved cable may be impossible to move through the receiving hole. The diameter of the receiving hole in the tool body must be closely dimensioned to match the outer diameter of the coaxial cable to keep the slitting blade in the correct position and a curved cable may tend to jam in the receiving hole.
A related problem also occurs, to a lesser extent, in improved tools having two hinged body halves. In these designs, each half of the body includes half of the receiving hole. Although the cable does not normally jam in either half, it tends to rise up away from the guiding surface and the shaving blade, preventing complete removal of the excess web material and accurate shaving. Because of the shape of the guiding surface on earlier tools, which prevents slightly curved cable from lying flat, and because the shaving blade of earlier tools is not adjustable, it is not always possible to properly shave the surface of the coaxial cable, particularly on a slightly curved or bent cable.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a combination cable slitting and shaving tool that produces a defect-free cylindrical coaxial cable exterior surface without flats or ridges.
It is another object of the present invention to provide a combination cable slitting and shaving tool that accurately follows and shaves the web from curved and straight coaxial cables without damaging the cable and without leaving any excess web material.
A further object of the invention is to provide a combination cable slitting and shaving tool that remains closed for storage and opens for insertion of the cable and for slitting the web at intermediate locations along the length of a messengered cable.
It is yet another object of the present invention to provide a combination cable slitting and shaving tool that protects the slitting blade when the tool is not in use and that prevents a user from inadvertently contacting the slitting or shaving blades.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects, which will be apparent to those skilled in art, are achieved in the present invention which is directed to a slitting and shaving tool for separating a first cable with a curved outer surface from a second cable. The tool includes a body and a hinge member, hinged to the body. The body is shaped so that it guides the tool to follow along one side of a web connecting the first cable to the second cable.
The hinge member moves between an open position in which it can receive the first cable and a closed position. The hinge member is shaped to cooperate with the body and guide the hinge member along an opposite side of the web from the body. The body and the hinge member hold a portion of the web between them when the hinge member is moved to the closed position.
The tool includes a slitting blade mounted on the tool and positioned to penetrate the web when the hinge member is moved to the closed position. The slitting blade cuts through the web and separates the first cable from the second cable as the tool is guided along the web by the body and the hinge member. The slitting blade cuts far enough away from the first cable to avoid damaging it and thereby leaves some excess web material on that cable.
The tool also includes a shaving blade with a curved cutting edge. The shaving blade is mounted to the body and shaves off the excess web material from the first cable to leave a smooth, defect-free, curved surface on the exterior of the first cable.
Preferably, the shaving blade is mounted to the body and the slitting blade is mounted on the hinge member. In the most highly preferred embodiment of the invention, the shaving blade is mounted on a ramp at an angle to the axis of the body and can be adjusted by sliding it up and down the ramp to adjust the depth of cut. The body includes a pair of side walls along the sides of the ramp surface that guide the shaving blade during adjustment and preventing it from twisting during shaving of the excess web material.
A spring is connected between the body and the hinge member to urge the hinge member towards the closed position. The body and the hinge member include squeeze tabs on opposite sides of the hinge line between the body and the hinge member to permit the hinge member to be moved to the open position by squeezing the squeeze tabs towards each other.
The body includes a relief hole with a curved perimeter allowing the excess web material shaved by the curved cutting edge to exit the tool. The relief hole is shaped with a curved perimeter so that the curve of the curved shaving blade cutting edge substantially matches the curve of the relief hole perimeter when the shaving blade is correctly adjusted.
The body of the tool includes a curved cable guide surface having a first radius circumferentially close to the shaving blade and a second larger radius circumferentially farther from the shaving blade to accommodate the first cable when the first cable is not straight.